Fluid pressure braking system



June 6, 1939. H. c. BOWEN 2,161,277

FLUID PRESSURE BRAKING SYSTEM Filed Jan. 8, 1937 f6 62 INVENTOR.

Hesse-er C. Ban aw M Wk M PAL-4 ATTORNEYS.

June 1 939 v 1 t I I I l UNITED STATES PATENT OFFICE Hafiz draulic BrakeCompany, Detroit, Mich, a corporation of California Application January3, 1937. semi No. 119,054

9 Claims. (01. 60-543) The invention relates to'fluid pressure brakofthe cylinder is a port 32 generally known as a ing systems, and moreparticularly to fluid prescompensating port. sure producing devices.Suitably connected to the discharge port 30 oi Broadly the inventioncomprehends a fluid the cylinder 24 is a fluid pressure delivery pipe or5 pressurebraking system including a pressure pro-, conduit 34 havingbranches 36, 38, 40 and 42 con- 6 ducing device operative tooverflll thesystem upnected respectively to fluid pressure actuated on completion ofeach braking operation-to the motors 44 arranged in pairs, one pair foractuend that any air or gas bubbles in the fluid may atlng the brakesassociated with the front wheels be expelled therefrom so as to insuremore satisof the vehicle andanother pair for actuating factory operationof the system. 5 I i the brakes associated with the rear wheels of 10 Anobject of the invention is to provide a fluid; the vehicle.

pressure braking system including a pressure Each of the brakespreferably includes a fixed producing device operative tooverflll-thesystem .support or backing plate 46, a rotatable drum 48upon completion of a braking operation. associated therewith, a pair ofcorresponding in- Another object of the invention is to provideterchangeable fric o elements Shoes 59 D a fluid pressure producingdevice including 9. cyled on the backing plate, and a fluid pressureactuinder, a piston movable therein, and means assoated motorcorresponding to the motors 44 mountciated with the cylinder and pistonfor pumping ed on the backing plate between the shoes and fluid.operativeto move the shoes into engagement Another object or theinvention is to provide with the drum against the resistance of a re- 20a fluid pressure producing device including a .tractile spring 5connecting the ShOeS- fluid reservoir, a cylinder supplied therefrom, aApiston 54 p e le in the cy 24 piston movable in the cylinder, and anexpan'silud s ahead 56 fitt d snu ly 'th y d a d ble chamber associated.therewith adapted to' a redillced body portion 58 providing in conjunc-25 draw fluid from the reservoir on the compression lon, w th v the we lof the cylinder an" annul 25 stroke of the piston. and to dischargefluid into a b v iil- The head has a p urality of sp c the cylinderforward of thepiston upoh comple P 3 8 8 Ports 52 Providing mmunicati ntion oi the retraction stroke "or the piston. 1 e weenit e'an u a ch b50 d t a portion Other objects'and advantages of the invention 3 0 t i rforw r f h D S n- A 001- so will appear from the followingdescrlptiontaken f laps blele -i' p 64 s ated o t e head of 80 inconnection with,the drawing forming a part h p st t s t e pa and a spr nof this specification, and m whi h, -66 interposed between the cup andthe head of Fig. 1 is a, diagrammatical illu tration a the cylinder.serves to retain the cup against disfluid pressure braking systemembodying t placement and also to return the piston to its revention;and I tracted position. 35

Fig. 2 is a vertical, sectional view of the fluid An annular-washer 68sleeved on the reduced pressure producing device. body portion 58 of thepiston is retained against Referring to the drawing for more speciflcded c ent by a rin 0 ea e in a u fe tails of the invention, l0represents a fluid reserentiel groove in t Wa Of t cylinder. i

voir having a removable top l2 provided with a hfl eplllrelity 1' spacedpass s P ts 40 filling opening normally closed as by a cap l4 12providing communications between the reserhaving suitable openings iifor venting the r ervoir Ill and the annular chamber 60. A collapsiblevoir to the atmosphere. The reservoir also has a leak-Pr fi D encirclingthe reduced y drain opening 18 normally closed as by a plug :0, portion58 of the piston and seating on the anand arranged in the wall of thereservoir admile! W s e 58 controls the Ports A Sp ng 45 jacent itsbottom is an opening 22. I6 interposed between the cup I4 and the back Acylinder 24 fittedsnugly in the opening 22 of thehead 56 of the pistonserves to retain the has a flange 26 suitably secured to the wall of cupagainst displacement and also provides a the reservoir so as to retainthe cylinder against seat for the piston when in its retracted position.

displacement. As shown, the cylinder is suspend- 1 A thrust block I8 issuitably secured to the 50 ed in the reservoir in parallel relation toand adpiston. As shown, the thrust block has a conjacent the bottom ofthe reservoir. One end of centric extension 80 threaded in an axialrethecylinder is closed as by e head 28 provided cess or bore in thereduced body portion 58 of with a discharge port It, and the other endof the piston. This thrust block has a greater dithe cylinder opens intothe reservoir. In thewall ameter than the diameter of the reduced body66' portion 58 providing an annular seat 82 adapted to receive andsupport the annular washer 88 during the compression stroke of thepiston.

' A shaft 84 mounted in the wall of the reservoir has suitably securedthereto within the reservoir an actuator 88 engaging the thrust block 18by line contact, and secured to the shaft outside the reservoir is anarm 88 connected as by a rod 88 to a foot pedal lever 92 pivoted on asupport 94 and connected by a retractile spring 98 to a fixed support98.

Assuming that'the system is properly installed in a motor vehicle andfilled with a suitable fluid or liquid, under these conditions, upondepressing the foot pedal lever 92 force is transmitted from the leverthrough the rod 98, the arm 88, the shaft 84 andthe actuator 88 to thepiston 54, resulting in moving the piston on its compression stroke.

During the initial movement of the piston on its compression stroke, thecup 84 on the head of the piston covers the compensating port 32, and,thereafter, as the piston advances, the fluid in the cylinder 24 forwardof the piston is displaced therefrom. Also, during the initial movementof the piston the restricted body portion 58 of the piston moves throughthe washer 68 seated on the retaining spring 18 and the collapsible cup14 held on the washer by the spring I8. a

The relative movement of the piston 54 and the cup 14 results inincreasing the capacity of the chamberv 88. This increase in capacitycauses a partial vacuum in the chamber 88, resulting in collapse of thecup 14 and in drawing fluid from the reservoir l8 through the ports I2in the washer 88 past the cup 14 into the chamber 88, completely fillingthe chamber 88 to its maximum increased capacity; whereupon the thrustblock 18 engages the washer 88 and carries the washer and cup during theremainder of the forward stroke of the piston.

During the compression stroke of the piston the fluid displaced from thecylinder 24 passes through the discharge port 38 and the fluid pressuredelivery pipe 34 and its respective branches 4 into the fluid pressureactuated motors 44, causing actuation of the motors. This actuation ofthe motors causes'movement of the friction elements or shoes 58 intoengagement with the braking surface of the drums 48 against theresistance of the retractile springs 52, and this re- 4 sults ineffectively retarding rotation of the drums.

Upon completion of a braking operation, the foot pedal lever 92 isreleased. whereupon the pedal is returned to its retracted positionunder the influence of the retractile spring 98. As the foot pedal leverreturns to its retracted position,

the actuator 88 connected to the lever by the rod 98, the arm 88, andthe shaft 84 is retracted. This results in release of the piston 54,whereupon the spring 88 becomes effective to return the piston to itsretracted position; and as the piston returns to its retracted positionfluid is returned from the fluid pressure delivery pipe or conduit itscompression stroke before the cup 84 on the head of the pistoncompletely covers the port. To compensate for this slight insufliciencyof fluid to completely fill the cylinder, as the piston moves to itsretracted position wherein it is balanced between the springs 88' and18, a partial vacuum is produced in the cylinder 24 forward of the headof the piston. This results in drawing a slight quantity of fluid fromthe chamber 88 through the ports 82 in the head'of the piston past thecollapsible cup 84 into that portion of the cylinder forward of thepiston, and just before the piston assumes its fully retracted positionthe washer 88 supporting the cup 14 seats on the retaining ring 18. Thiscauses relative movement between the piston and the cup 14 resulting incontracting the chamber 88 to its minimum capacity, and as the capacityof the chamber is reduced to its minimum capacity a suflicient quantityof fluid is displaced therefrom through the ports 82 in the head of thepiston 54 to overfill the cylinder 24. This surplus of fluid in thesystem passes from the cylinder 24 through the compensating port 32 intothe reservoir l8 and carries with it any gas or air bubbles that may bepresent in the fluid. This overfllling of the cylinder 24 takes'place atthe conclusion of each brake operation, hence the system is maintainedfull of fluid and the fluid in the system is maintained free from gas orair bubbles.

Although this invention has been described in connection with certainspecific embodiments, the principles involved are susceptible ofnumerous other applications that will readily ocour to persons skilledin the art. The invention is, therefore, to be limited only by the scopeof the appended claims. I

Having thus described the various features of the invention, what Iclaim as new and desire to secure by Letters Patent is,

1. A fluid pressure producing device comprising a cylinder of uniformdiameter throughout, a piston reciprocable therein, a variable chamberback of the piston, means for introducing fluid into the chamber onthecompression stroke of the piston, and means including a floatingpiston for displacing fluid from the chamber on the retraction stroke ofthe piston.

2. A fluid pressure producing device comprising a reservoir, a cylindersupplied therefrom, a piston reciprocable in the cylinder, a variablechamber and floating piston means between the piston and the reservoirdrawing fluid from the reservoir on the compression stroke of the pistonand displacing fluid therefrom into that portion of the cylinder forwardof the piston on the retraction stroke of the piston, means forreciprocating said first named piston independently of said floatingpiston, and a lost motion connection between -said pistons. I

3. A pressure producing device comprising a. reservoir, a cylindersupplied therefrom, said cylinder being of uniform diameter throughout,a piston reciprocable in thecylinder, a variable chamber back of thepiston communicating with the reservoir and that portion of the cylinderforward of the piston, and means including a floating piston controllingthe communications so as to provide for passage of fluid from thereservoir into the cylinder "on the compression stroke of the piston andthe displacement of fluid from the chamber into the cylinder forward ofthe piston when the piston returns to its retracted position.

4. A fluid pressure producing device comprising a reservoir, a cylindersupplied therefrom, a piston reciprocable in the cylinder, a chamberback of the piston having ports communicating with the reservoir andwith that portion of the cylinder forward of the piston and meansincluding a floating piston controlling the ports operative to admit thepassage of fluid from the reservoir to the chamber on the compressionstroke of the piston and to displace fluid from the chamber into thatportion of the cylinder forward of the piston on the return stroke ofthe piston, means for operating said first named piston, and aconnection between said pistons whereby movement of said first namedpiston through a predetermined distance produces movement of saidfloating piston,

5. A fluid pressure producing device comprising a reservoir, a cylindersupplied therefrom.

\ piston reciprocable in the cylinder having a re- 7. In a fluidpressure braking system a fluid pressure producing device comprising areservoir, a cylinder supplied therefrom, a piston reciprocable thereinand having a reduced body portion, means movable on said reduced bodyportion for varying the volume of the chamber formed between said meansand said piston, means tending to enlarge the volume of said variablechamber, means carried by the piston for unidirectionally controllingthe flow of liquid past said piston, and means movable on the reducedbody portion of said piston for unidirectionally controlling the flow ofliquid past the last-named means movable on the reduced body portion forvarying the volume of the chamber formed between this means and saidpiston.

8. In a fluid pressure braking system a fluid pressure producing devicecomprising a reservoir, a cylinder supplied therefrom, said cylinderbeing of uniform diameter, a piston reciprocable therein and having areduced body, portion, means for unidirectionally controlling the flowof liquid past said piston, means movable on said. reduced body portionfor forcing a quantity of fluid past the aforesaid means when the pistonis returning to a position prior to its next fluid compressive movement.

9. A fluid pressure producing device comprising a reservoir, a cylindersupplied therefrom, a piston reciprocable in the cylinder having areduced body portion, a variable annular chamber back of the pistonhaving ports providing communications between the chamber and thatportion of the cylinder forward of the piston, a collapsible leak-proofcup on the head of the piston controlling the ports, a closure for theannular chamber movable on the reduced body portion of the piston havingports providing communi cations between the chamber and the reservoir, acollapsible leak-proof cup on the closure controlling the ports therein,elastic means bearing on said closure and said piston, and meansfastened to the aforesaid reduced body portion for causing said closureto follow the movement oi said piston while the liquid in front of saidpiston is under compression.

HERBERT C. BOWEN.

